In the acid treatment of subterranean formations penetrated by a wellbore, an aqueous acid solution is injected down the well into the formation to dissolve formation materials and/or other materials deposited in the wellbore thereby improving permeability of the formation and its production. The acid treatment may be carried out under matrix injection rates or fracturing rates.
A serious problem associated with acidizing formations is the high corrosivity of the acid solution on surface and subsurface metal equipment. The acid, normally HCl or mud acid (HCl-HF mixture), is highly corrosive to ferrous metals. Accordingly, the acid treatment almost always involves the use of corrosion inhibitors.
Corrosion inhibitors used in the past in acid treatment of wells include various acetylenic alcohols, fluorinated surfactants, quaternary derivatives of heterocyclic nitrogen bases and halomethylated aromatic compounds, formamides and surface active agents, alone or in combination with other materials. Examples of these prior art corrosion inhibitors are disclosed in U.S. Pat. Nos. 3,658,720 and 4,028,268.